Neurological and psychiatric symptoms such as fatigue and depression are common among people with coronavirus and may be just as likely in people with mild cases, new research suggests.

Evidence from 215 studies of Covid-19 indicates a wide range of ways in which Covid-19 can affect mental health and the brain.

The studies from 30 countries involved a total of 105,638 people with acute symptoms (the main disease stage, rather than longer-term impacts) of Covid-19, including data up to July 2020.

Lead author Dr Jonathan Rogers, of UCL Psychiatry and South London and Maudsley NHS Foundation Trust, said: “We had expected that neurological and psychiatric symptoms would be more common in severe Covid-19 cases, but instead we found that some symptoms appeared to be more common in mild cases.

“It appears that Covid-19 affecting mental health and the brain is the norm, rather than the exception.”

Across the dataset, the most common neurological and psychiatric symptoms were anosmia – loss of smell – reported by 43% of patients with the disease, weakness (40%), fatigue (38%), loss of taste (37%), muscle pain (25%), depression (23%), headache (21%) and anxiety (16%).

Major neurological disorders such as ischaemic stroke (1.9% of cases in the dataset), haemorrhagic stroke (0.4%) and seizure (0.06%) were also identified.

Patients with severe Covid-19 were overrepresented in the dataset, as most of the studies focused on patients admitted to hospital, and even the studies of people outside hospitals included few with very mild or no symptoms.

However, the study published in the Journal of Neurology, Neurosurgery and Psychiatry, found that among people with symptomatic acute Covid-19 who were not admitted to hospital, neurological and psychiatric symptoms were still common.

The data indicated that 55% reported fatigue, 52% loss of smell, 47% muscle pain, 45% loss of taste, and 44% reported headaches.

The researchers said it is still possible that such symptoms are just as common in severe cases, as mild symptoms might not be reported by a patient in critical care.

While the review did not investigate causal mechanisms, the researchers suggested a few possible explanations.

In the acute phase of the illness, inflammation has been found in the brain, which may explain some of the symptoms.

Psychosocial factors relating to the context of the global pandemic may also play a role, researchers suggested.

This might be because people who are acutely ill may feel isolated when they cannot see their family or friends, which may explain why depression and anxiety have been found in some Covid-19 studies to be more common than in other viral illnesses such as the flu.

Dr Rogers said: “Many factors could contribute to neurological and psychiatric symptoms in the early stages of infection with Covid-19, including inflammation, impaired oxygen delivery to the brain, and psychological factors. More studies are needed to understand these links better.”

Joint senior author Dr Alasdair Rooney, from the University of Edinburgh, said: “Neurological and psychiatric symptoms are very common in people with Covid-19.

“With millions of people infected globally, even the rarer symptoms could affect substantially more people than in usual times.

“Mental health services and neurological rehabilitation services should be resourced for an increase in referrals.”

– The study was led by researchers at UCL, the University of Edinburgh, King’s College London and Queen Mary University of London, with co-authors in the UK, Bulgaria, Canada, India and Germany.